1. Technical Field
The present invention relates to vehicle controllers, and more particularly, to the prevention of rapid acceleration unintended by a driver during a transition from a poor road travel mode, in which a rate at which an output increases relative to an accelerator operation during an initial stage of the accelerator operation is suppressed, to another travel mode.
2. Related Art
An apparatus with which various types of control, such as engine characteristic control and shift characteristic control, can be selected from a plurality of modes in accordance with preferences of a driver and a vehicle use condition has been proposed for use in a vehicle such as an automobile.
For example, it has been proposed that a sport travel mode or the like, in which shift control is modified such that a rate at which an engine torque increases in response to an accelerator operation is increased, and in which the engine is more likely to be used at a comparatively high rotation speed, be provided in addition to a normally used vehicle control mode, and that a driver be able to perform an operation to switch between the respective modes.
Conventional vehicle control mode switching includes a technique disclosed in Japanese Unexamined Patent Application Publication (JP-A) No. H11-198677. According to the technique, in a vehicle that performs adaptive cruise control (ACC) for maintaining a predetermined inter-vehicle distance to a leading vehicle, adaptive cruise control processing is terminated when it is determined, on the basis of an operation of an antilock brake control device, that the vehicle is traveling on a road surface having a low frictional coefficient such as a snowy road or a frozen road.
Further, a technique disclosed in JP-A No. H2-127156 provides a low speed travel mode in which a brake is operated in conjunction with an accelerator OFF operation, the low speed travel mode being canceled automatically when a cancellation condition relating to a vehicle speed or the like is established.
It has been proposed recently that a poor road travel mode, in which the engine torque increase rate during the initial stage of the accelerator operation is suppressed in comparison with the vehicle travel mode used during normal travel, be provided in an SUV vehicle or the like, in which importance is placed on a travel performance on poor roads, in order to improve operability during travel on poor roads.
However, a vehicle may have a plurality of normal travel modes with different output characteristics relative to the accelerator operation, and when, in such a vehicle, a transition is performed from the poor road travel mode to a normal travel mode, from among the plurality of normal travel modes, in which the output characteristic during the initial stage of the accelerator operation is dramatically different to that of the poor road travel mode, a high output unintended by the driver may be generated, causing the vehicle to accelerate rapidly.